1. Field of the Invention
The present invention relates generally to a cassette loading apparatus and, more particularly, to a cassette loading apparatus having a driving gear for use with a front-loading type video tape recorder.
2. Description of the Background
Japanese Patent Application No. 62-78746 having the same assignee as the instant application describes a cassette holder locking mechanism for locking a cassette holder when it is moved to the loading position in a front-loading type video tape recorder. FIG. 1 is a pictorial representation of such a locking mechanism for a cassette holder that has been previously proposed.
As shown in FIG. 1, this cassette holder locking mechanism is comprised of a drive gear 1 and a follower gear 2, each of drive gear 1 and follower gear 2 being only so-called segment gears. Drive gear 1 is provided at an outer peripheral portion thereof with a worm gear 3 that is driven by a motor 8, whereas follower gear 2 is provided with a drive arm 4 that moves a pin arranged at the side walls of a cassette holder (not shown). When drive gear 1 is driven by motor 8 through worm gear 3, follower gear 2 is driven by drive gear segment 1, so that drive arm 4 pushes the pin of the cassette holder, whereby the cassette holder is moved to a predetermined loading position.
In the arrangement of the elements shown in FIG. 1, the cassette holder is also locked by the above-described drive mechanism by using a protrusion 6 provided on follower gear 2 that is received by a guide rib 7 provided on drive gear 1. More specifically, the cassette holder is held by this locking mechanism when follower gear 2 produces a rotational force in the direction shown by arrow 5 and this rotational force is received by guide rib 7 of drive gear 1 through protrusion 6. Then, the rotational force of follower gear 2 is received by drive gear 1 via protrusion 6 and guide rib 7, whereby follower gear 2 is prevented from being rotated.
It is to be noted that the locking mechanism of this previously proposed cassette loading apparatus has the following problems associated with it. In the initial stage where the tape cassette is moved to the loading position when the tape cassette is loaded on the cassette holder, drive gear 1 and follower gear 2 are driven while being meshed with each other, however, if drive gear 1 and follower gear 2 are disengaged from each other and can not be meshed with each other, then protrusion 6 is pushed by guide rib 7 of drive gear 1, thereby effecting the locked state shown in FIG. 1. When the gear pair formed of drive gear 1 and follower gear 2 are not meshed with each other, the two gears are free to have independent, random rotation, so that when the gears become meshed again they will be at positions other than the correct position.
Further, if the tape cassette has been loaded in the cassette compartment and the power switch is turned OFF, then it is frequently the case that the tape cassette is ejected because the locked condition is not yet effected. Furthermore, the locked condition depends on the design or accuracy of cams in the locking portion so that satisfactory efficiency of the locking mechanism can not be maintained without difficulty.